1. The problem statement, all variables and given/known data A uniform wheel of mass 10.0kg and radius 0.400m is mounted rigidly on a massless axle through its centre. The radius of the axle is 0.200m, and the rotational inertia of the wheel-axle combination about its central axis is 0.600kg.m2. The wheel is initially at rest at the top of a surface that is inclined at an angle of 30.0o with the horizontal; the axle rests on the surface while the wheel extends into a groove in the surface without touching the surface. Once released, the axle rolls down along the surface smoothly and without slipping. When the wheel-axle combination has moved down the surface by 2.00m, what are (a) its rotational kinetic energy and (b) its translational kinetic energy? 2. Relevant equations 3. The attempt at a solution The COM of the wheel drops a distance of h = mgsin30o = 1.00m, so the gain in kinetic energy is: [tex]\Delta[/tex]K = mgh = 10.0(9.80)(1.00) = 98.0J and [tex]\Delta[/tex]K = 0.5mV2 + 0.5I[tex]\omega[/tex]2 So this is where things became sticky. I took the force due to gravity to be acting at the COM, and with the radius of the axle I arrived at a torque of mgsin30o(0.200) = 9.8N.m. Dividing this by the given rotational inertia I get [tex]\alpha[/tex] = 16.3rad/s2. Next, the axle has a circumference of 0.4[tex]\pi[/tex], and with the 2.00m travelled I get an angular displacement of 10rad. In the end, plugging these values into the usual energy equations do not yield the correct answer for (a). I suspect I made a balls of it somewhere with the torque. Sorry about the rotten format folks. As my name indicates , I am but a noob here and I haven't gotten the hang of LaTex yet.